RNA m6A Methyltransferase Mettl3 Regulates Spatial Neural Patterning in Xenopus laevis.

N6-Methyladenosine (m6A) is the most prevalent internal RNA modification and has a widespread impact on mRNA stability and translation. Methyltransferase-like 3 (Mettl3) is a methyltransferase responsible for RNA m6A modification, and it is essential for early embryogenesis before or during gastrulation in mice and zebrafish. However, due to the early embryonic lethality, loss-of-function phenotypes of Mettl3 beyond gastrulation, especially during neurulation stages when spatial neural patterning takes place, remain elusive. Here, we address multiple roles of Mettl3 during Xenopus neurulation in anteroposterior neural patterning, neural crest specification, and neuronal cell differentiation. Knockdown of Mettl3 causes anteriorization of neurulae and tailbud embryos along with the loss of neural crest and neuronal cells. Knockdown of the m6A reader Ythdf1 and mRNA degradation factors, such as 3' to 5' exonuclease complex component Lsm1 or mRNA uridylation enzyme Tut7, also show similar neural patterning defects, suggesting that m6A-dependent mRNA destabilization regulates spatial neural patterning in Xenopus. We also address that canonical WNT signaling is inhibited in Mettl3 morphants, which may underlie the neural patterning defects of the morphants. Altogether, this study reveals functions of Mettl3 during spatial neural patterning in Xenopus.